Regenerate.

(Logical change 1.148)

doc/libunwind-dynamic.man

@@ -1,5 +1,5 @@
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-.\" Manual page created with latex2man on Tue Dec  9 23:06:06 PST 2003
+.\" Manual page created with latex2man on Sat Dec 20 22:00:11 PST 2003
 .\" NOTE: This file is generated, DO NOT EDIT.
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@@ -10,7 +10,7 @@
 
 .fi
 ..
-.TH "LIBUNWIND\-DYNAMIC" "3" "09 December 2003" "Programming Library " "Programming Library "
+.TH "LIBUNWIND\-DYNAMIC" "3" "20 December 2003" "Programming Library " "Programming Library "
 .SH NAME
 libunwind\-dynamic
 \-\- libunwind\-support for runtime\-generated code 
@@ -19,62 +19,74 @@ libunwind\-dynamic
 
 .PP
 For libunwind
-to do its work, it needs to be able to 
+to do its job, it needs to be able to reconstruct 
-reconstruct the \fIframe state\fP
+the \fIframe state\fP
-of each frame in a call\-chain. The 
+of each frame in a call\-chain. The frame state 
-frame state consists of some frame registers (such as the 
+describes the subset of the machine\-state that consists of the 
-instruction\-pointer and the stack\-pointer) and the locations at which 
+\fIframe registers\fP
-the current values of every callee\-saved (``preserved\&'') resides. 
+(typically the instruction\-pointer and the 
+stack\-pointer) and all callee\-saved registers (preserved registers). 
+The frame state describes each register either by providing its 
+current value (for frame registers) or by providing the location at 
+which the current value is stored (callee\-saved registers). 
 .PP
-The purpose of the dynamic unwind\-info is therefore to provide 
+For statically generated code, the compiler normally takes care of 
+emitting \fIunwind\-info\fP
+which provides the minimum amount of 
+information needed to reconstruct the frame\-state for each instruction 
+in a procedure. For dynamically generated code, the runtime code 
+generator must use the dynamic unwind\-info interface provided by 
 libunwind
-the minimal information it needs about each 
+to supply the equivalent information. This manual 
-dynamically generated procedure such that it can reconstruct the 
+page describes the format of this information in detail. 
-procedure\&'s frame state. 
 .PP
-For the purpose of the following discussion, a \fIprocedure\fP
+For the purpose of this discussion, a \fIprocedure\fP
-is any 
+is defined to 
-contiguous piece of code. Normally, each procedure directly 
+be an arbitrary piece of \fIcontiguous\fP
-corresponds to a function in the source\-language but this is not 
+code. Normally, each 
-strictly required. For example, a runtime code\-generator could 
+procedure directly corresponds to a function in the source\-language 
-translate a given function into two separate (discontiguous) 
+but this is not strictly required. For example, a runtime 
-procedures: one for frequently\-executed (hot) code and one for 
+code\-generator could translate a given function into two separate 
-rarely\-executed (cold) code. Similarly, simple source\-language 
+(discontiguous) procedures: one for frequently\-executed (hot) code and 
-functions (usually leaf functions) may get translated into code for 
+one for rarely\-executed (cold) code. Similarly, simple 
-which the default unwind\-conventions apply and for such code, no 
+source\-language functions (usually leaf functions) may get translated 
-dynamic unwind info needs to be registered. 
+into code for which the default unwind\-conventions apply and for such 
+code, it is not strictly necessary to register dynamic unwind\-info. 
 .PP
-Within a procedure, the code can be thought of as being divided into a 
+A procedure logically consists of a sequence of \fIregions\fP\&.
-sequence of \fIregions\fP\&.
+Regions are nested in the sense that the frame state at the end of one 
-Each region logically consists of an 
+region is, by default, assumed to be the frame state for the next 
-optional \fIprologue\fP,
+region. Each region is thought of as being divided into a 
+\fIprologue\fP,
 a \fIbody\fP,
-and an optional 
+and an \fIepilogue\fP\&.
-\fIepilogue\fP\&.
+Each of them 
-If present, the prologue sets up the frame state for 
+can be empty. If non\-empty, the prologue sets up the frame state for 
-the body, which does the actual work of the procedure. For example, 
+the body. For example, the prologue may need to allocate some space 
-the prologue may need to allocate a stack\-frame and save some 
+on the stack and save certain callee\-saved registers. The body 
-callee\-saved registers before the body can start executing. 
+performs the actual work of the procedure but does not change the 
-Correspondingly, the epilogue, if present, restores the previous frame 
+frame state in any way. If non\-empty, the epilogue restores the 
-state and thereby undoes the effect of the prologue. Regions are 
+previous frame state and as such it undoes or cancels the effect of 
-nested in the sense that the frame state at the end of a region serves 
+the prologue. In fact, a single epilogue may undo the effect of the 
-as the entry\-state of the next region. At the end of several nested 
+prologues of several (nested) regions. 
-regions, there may be a single epilogue which undoes the effect of all 
-the prologues in the nested regions. 
 .PP
-Even though logically we think of the prologue, body, and epilogue as 
+We should point out that even though the prologue, body, and epilogue 
-separate entities, optimizing code\-generators will generally 
+are logically separate entities, optimizing code\-generators will 
-interleave instructions from all three entities to achieve higher 
+generally interleave instructions from all three entities. For this 
-performance. In fact, as far as the dynamic unwind\-info is concerned, 
+reason, the dynamic unwind\-info interface of libunwind
-there is no distinction at all between prologue and body. Similarly, 
+makes no 
-the exact set of instructions that make up an epilogue is also 
+distinction whatsoever between prologue and body. Similarly, the 
-irrelevant. The only point in the epilogue that needs to be described 
+exact set of instructions that make up an epilogue is also irrelevant. 
-explicitly is the point at which the stack\-pointer gets restored. The 
+The only point in the epilogue that needs to be described explicitly 
-reason this point needs to be described is that once the stack\-pointer 
+by the dynamic unwind\-info is the point at which the stack\-pointer 
-is restored, all values saved in the deallocated portion of the stack 
+gets restored. The reason this point needs to be described is that 
-become invalid. All other locations that store the values of 
+once the stack\-pointer is restored, all values saved in the 
-callee\-saved register are assumed to remain valid throughout the end 
+deallocated portion of the stack frame become invalid and hence 
-of the region. 
+libunwind
+needs to know about it. The portion of the frame 
+state not saved on the stack is assume to remain valid through the end 
+of the region. For this reason, there is usually no need to describe 
+instructions which restore the contents of callee\-saved registers. 
 .PP
 Within a region, each instruction that affects the frame state in some 
 fashion needs to be described with an operation descriptor. For this 
@@ -93,42 +105,399 @@ in the stack frame.
 .SH PROCEDURES
 
 .PP
+A runtime code\-generator registers the dynamic unwind\-info of a 
+procedure by setting up a structure of type unw_dyn_info_t
+and calling _U_dyn_register(),
+passing the address of the 
+structure as the sole argument. The members of the 
 unw_dyn_info_t
-unw_dyn_proc_info_t 
+structure are described below: 
-unw_dyn_table_info_t 
+.TP
-unw_dyn_remote_table_info_t 
+void *next
+ Private to libunwind\&.
+Must not be used 
+by the application. 
+.TP
+void *prev
+ Private to libunwind\&.
+Must not be used 
+by the application. 
+.TP
+unw_word_t start_ip
+ The start\-address of the 
+instructions of the procedure (remember: procedure are defined to be 
+contiguous pieces of code, so a single code\-range is sufficient). 
+.TP
+unw_word_t end_ip
+ The end\-address of the 
+instructions of the procedure (non\-inclusive, that is, 
+end_ip\-start_ip
+is the size of the procedure in 
+bytes). 
+.TP
+unw_word_t gp
+ The global\-pointer value in use 
+for this procedure. The exact meaing of the global\-pointer is 
+architecture\-specific and on some architecture, it is not used at 
+all. 
+.TP
+int32_t format
+ The format of the unwind\-info. 
+This member can be one of UNW_INFO_FORMAT_DYNAMIC,
+UNW_INFO_FORMAT_TABLE,
+or 
+UNW_INFO_FORMAT_REMOTE_TABLE\&.
+.TP
+union u
+ This union contains one sub\-member 
+structure for every possible unwind\-info format: 
+.RS
+.TP
+unw_dyn_proc_info_t pi
+ This member is used 
+for format UNW_INFO_FORMAT_DYNAMIC\&.
+.TP
+unw_dyn_table_info_t ti
+ This member is used 
+for format UNW_INFO_FORMAT_TABLE\&.
+.TP
+unw_dyn_remote_table_info_t rti
+ This member 
+is used for format UNW_INFO_FORMAT_REMOTE_TABLE\&.
+.RE
+.RS
 .PP
-.SH REGIONS
+The format of these sub\-members is described in detail below. 
+.RE
+.PP
+.SS PROC\-INFO FORMAT
+.PP
+This is the preferred dynamic unwind\-info format and it is generally 
+the one used by full\-blown runtime code\-generators. In this format, 
+the details of a procedure are described by a structure of type 
+unw_dyn_proc_info_t\&.
+This structure contains the following 
+members: 
+.PP
+.RE
+.TP
+unw_word_t name_ptr
+ The address of a 
+(human\-readable) name of the procedure or 0 if no such name is 
+available. If non\-zero, The string stored at this address must be 
+ASCII NUL terminated. For source languages that use name\-mangling 
+(such as C++ or Java) the string stored at this address should be 
+the \fIdemangled\fP
+version of the name. 
+.PP
+.TP
+unw_word_t handler
+ The address of the 
+personality\-routine for this procedure. Personality\-routines are 
+used in conjunction with exception handling. See the C++ ABI draft 
+(http://www.codesourcery.com/cxx\-abi/) for an overview and a 
+description of the personality routine. If the procedure has no 
+personality routine, handler
+must be set to 0. 
+.PP
+.TP
+uint32_t flags
+ A bitmask of flags. At the 
+moment, no flags have been defined and this member must be 
+set to 0. 
+.PP
+.TP
+unw_dyn_region_info_t *regions
+ A NULL\-terminated 
+linked list of region\-descriptors. See section ``Region 
+descriptors\&'' below for more details. 
+.PP
+.SS TABLE\-INFO FORMAT
+.PP
+This format is generally used when the dynamically generated code was 
+derived from static code and the unwind\-info for the dynamic and the 
+static versions is identical. For example, this format can be useful 
+when loading statically\-generated code into an address\-space in a 
+non\-standard fashion (i.e., through some means other than 
+dlopen()).
+In this format, the details of a group of procedures 
+is described by a structure of type unw_dyn_table_info\&.
+This structure contains the following members: 
+.PP
+.TP
+unw_word_t name_ptr
+ The address of a 
+(human\-readable) name of the procedure or 0 if no such name is 
+available. If non\-zero, The string stored at this address must be 
+ASCII NUL terminated. For source languages that use name\-mangling 
+(such as C++ or Java) the string stored at this address should be 
+the \fIdemangled\fP
+version of the name. 
+.PP
+.TP
+unw_word_t segbase
+ The segment\-base value 
+that needs to be added to the segment\-relative values stored in the 
+unwind\-info. The exact meaning of this value is 
+architecture\-specific. 
+.PP
+.TP
+unw_word_t table_len
+ The length of the 
+unwind\-info (table_data)
+counted in units of words 
+(unw_word_t).
+.PP
+.TP
+unw_word_t table_data
+ A pointer to the actual 
+data encoding the unwind\-info. The exact format is 
+architecture\-specific (see architecture\-specific sections below). 
+.PP
+.SS REMOTE TABLE\-INFO FORMAT
+.PP
+The remote table\-info format has the same basic purpose as the regular 
+table\-info format. The only difference is that when libunwind
+uses the unwind\-info, it will keep the table data in the target 
+address\-space (which may be remote). Consequently, the type of the 
+table_data
+member is unw_word_t
+rather than a pointer. 
+This implies that libunwind
+will have to access the table\-data 
+via the address\-space\&'s access_mem()
+call\-back, rather than 
+through a direct memory reference. 
+.PP
+From the point of view of a runtime\-code generator, the remote 
+table\-info format offers no advantage and it is expected that such 
+generators will describe their procedures either with the proc\-info 
+format or the normal table\-info format. The main reason that the 
+remote table\-info format exists is to enable the 
+address\-space\-specific find_proc_info()
+callback (see 
+unw_create_addr_space(3))
+to return unwind tables whose 
+data remains in remote memory. This can speed up unwinding (e.g., for 
+a debugger) because it reduces the amount of data that needs to be 
+loaded from remote memory. 
+.PP
+.SH REGIONS DESCRIPTORS
 
 .PP
-unw_dyn_region_info_t: 
+A region descriptor is a variable length structure that describes how 
-\- insn_count can be negative to indicate that the region is 
+each instruction in the region affects the frame state. Of course, 
-at the end of the procedure; in such a case, the negated 
+most instructions in a region usualy do not change the frame state and 
-insn_count value specifies the length of the final region 
+for those, nothing needs to be recorded in the region descriptor. A 
-in number of instructions. There must be at most one region 
+region descriptor is a structure of type 
-with a negative insn_count and only the last region in a 
+unw_dyn_region_info_t
-procedure\&'s region list may be negative. Furthermore, both 
+and has the following members: 
-di\->start_ip and di\->end_ip must be valid. 
+.TP
+unw_dyn_region_info_t *next
+ A pointer to the 
+next region. If this is the last region, next
+is NULL\&.
+.TP
+int32_t insn_count
+ The length of the region in 
+instructions. Each instruction is assumed to have a fixed size (see 
+architecture\-specific sections for details). The value of 
+insn_count
+may be negative in the last region of a procedure 
+(i.e., it may be negative only if next
+is NULL).
+A 
+negative value indicates that the region covers the last \fIN\fP
+instructions of the procedure, where \fIN\fP
+is the absolute value 
+of insn_count\&.
+.TP
+uint32_t op_count
+ The (allocated) length of 
+the op_count
+array. 
+.TP
+unw_dyn_op_t op
+ An array of dynamic unwind 
+directives. See Section ``Dynamic unwind directives\&'' for a 
+description of the directives. 
 .PP
-.SH OPERATIONS
+A region descriptor with an insn_count
+of zero is an 
+\fIempty region\fP
+and such regions are perfectly legal. In fact, 
+empty regions can be useful to establish a particular frame state 
+before the start of another region. 
+.PP
+A single region list can be shared across multiple procedures provided 
+those procedures share a common prologue and epilogue (their bodies 
+may differ, of course). Normally, such procedures consist of a canned 
+prologue, the body, and a canned epilogue. This could be described by 
+two regions: one covering the prologue and one covering the epilogue. 
+Since the body length is variable, the latter region would need to 
+specify a negative value in insn_count
+such that 
+libunwind
+knows that the region covers the end of the procedure 
+(up to the address specified by end_ip).
+.PP
+The region descriptor is a variable length structure to make it 
+possible to allocate all the necessary memory with a single 
+memory\-allocation request. To facilitate the allocation of a region 
+descriptors libunwind
+provides a helper routine with the 
+following synopsis: 
+.PP
+size_t
+_U_dyn_region_size(int
+op_count);
+.PP
+This routine returns the number of bytes needed to hold a region 
+descriptor with space for op_count
+unwind directives. Note 
+that the length of the op
+array does not have to match exactly 
+with the number of directives in a region. Instead, it is sufficient 
+if the op
+array contains at least as many entries as there are 
+directives, since the end of the directives can always be indicated 
+with the UNW_DYN_STOP
+directive. 
+.PP
+.SH DYNAMIC UNWIND DIRECTIVES
 
 .PP
-unw_dyn_operation_t 
+A dynamic unwind directive describes how the frame state changes 
-unw_dyn_op_t 
+at a particular point within a region. The description is in 
+the form of a structure of type unw_dyn_op_t\&.
+This 
+structure has the following members: 
+.TP
+int8_t tag
+ The operation tag. Must be one 
+of the unw_dyn_operation_t
+values described below. 
+.TP
+int8_t qp
+ The qualifying predicate that controls 
+whether or not this directive is active. This is useful for 
+predicated architecturs such as IA\-64 or ARM, where the contents of 
+another (callee\-saved) register determines whether or not an 
+instruction is executed (takes effect). If the directive is always 
+active, this member should be set to the manifest constant 
 _U_QP_TRUE
+(this constant is defined for all 
+architectures, predicated or not). 
+.TP
+int16_t reg
+ The number of the register affected 
+by the instruction. 
+.TP
+int32_t when
+ The region\-relative number of 
+the instruction to which this directive applies. For example, 
+a value of 0 means that the effect described by this directive 
+has taken place once the first instruction in the region has 
+executed. 
+.TP
+unw_word_t val
+ The value to be applied by the 
+operation tag. The exact meaning of this value varies by tag. See 
+Section ``Operation tags\&'' below. 
 .PP
-unw_dyn_info_format_t 
+It is perfectly legitimate to specify multiple dynamic unwind 
+directives with the same when
+value, if a particular instruction 
+has a complex effect on the frame state. 
 .PP
-\- instructions don\&'t have to be sorted in increasing order of ``when\&'' 
+Empty regions by definition contain no actual instructions and as such 
-values: In general, if you can generate the sorted order easily 
+the directives are not tied to a particular instruction. By 
-(e.g., without an explicit sorting step), I\&'d recommend doing so 
+convention, the when
-because in that case, should some version of libunwind ever require 
+member should be set to 0, however. 
-sorted order, libunwind can verify in O(N) that the list is sorted 
+.PP
-already. In the particular case of the ia64\-version of libunwind, a 
+There is no need for the dynamic unwind directives to appear 
-sorted order won\&'t help, since it always scans the instructions up 
+in order of increasing when
-to UNW_DYN_STOP. 
+values. If the directives happen to 
+be sorted in that order, it may result in slightly faster execution, 
+but a runtime code\-generator should not go to extra lengths just to 
+ensure that the directives are sorted. 
+.PP
+IMPLEMENTATION NOTE: should libunwind
+implementations for 
+certain architectures prefer the list of unwind directives to be 
+sorted, it is recommended that such implementations first check 
+whether the list happens to be sorted already and, if not, sort the 
+directives explicitly before the first use. With this approach, the 
+overhead of explicit sorting is only paid when there is a real benefit 
+and if the runtime code\-generator happens to generated sorted lists 
+naturally, the performance penalty is limited to a simple O(N) check. 
+.PP
+.SS OPERATIONS TAGS
+.PP
+The possible operation tags are defined by enumeration type 
+unw_dyn_operation_t
+which defines the following 
+values: 
+.PP
+.TP
+UNW_DYN_STOP
+ Marks the end of the dynamic unwind 
+directive list. All remaining entries in the op
+array of the 
+region\-descriptor are ignored. This tag is guaranteed to have a 
+value of 0. 
+.PP
+.TP
+UNW_DYN_SAVE_REG
+ Marks an instruction which saves 
+register reg
+to register val\&.
+.PP
+.TP
+UNW_DYN_SPILL_FP_REL
+ Marks an instruction which 
+spills register reg
+to a frame\-pointer\-relative location. The 
+frame\-pointer\-relative offset is given by the value stored in member 
+val\&.
+See the architecture\-specific sections for a description 
+of the stack frame layout. 
+.PP
+.TP
+UNW_DYN_SPILL_SP_REL
+ Marks an instruction which 
+spills register reg
+to a stack\-pointer\-relative location. The 
+stack\-pointer\-relative offset is given by the value stored in member 
+val\&.
+See the architecture\-specific sections for a description 
+of the stack frame layout. 
+.PP
+.TP
+UNW_DYN_ADD
+ Marks an instruction which adds 
+the constant value val
+to register reg\&.
+To add subtract 
+a constant value, store the two\&'s\-complement of the value in 
+val\&.
+The set of registers that can be specified for this tag 
+is described in the architecture\-specific sections below. 
+.PP
+.TP
+UNW_DYN_POP_FRAMES
+ .PP
+.TP
+UNW_DYN_LABEL_STATE
+ .PP
+.TP
+UNW_DYN_COPY_STATE
+ .PP
+.TP
+UNW_DYN_ALIAS
+ .PP
+unw_dyn_op_t 
 .PP
-_U_dyn_region_info_size(opcount); 
 _U_dyn_op_save_reg(); 
 _U_dyn_op_spill_fp_rel(); 
 _U_dyn_op_spill_sp_rel(); 
@@ -139,6 +508,18 @@ _U_dyn_op_copy_state();
 _U_dyn_op_alias(); 
 _U_dyn_op_stop(); 
 .PP
+.SH IA\-64 SPECIFICS
+
+.PP
+\- meaning of segbase member in table\-info/table\-remote\-info format 
+\- format of table_data in table\-info/table\-remote\-info format 
+\- instruction size: each bundle is counted as 3 instructions, regardless 
+of template (MLX) 
+\- describe stack\-frame layout, especially with regards to sp\-relative 
+and fp\-relative addressing 
+\- UNW_DYN_ADD can only add to ``sp\&'' (always a negative value); use 
+POP_FRAMES otherwise 
+.PP
 .SH SEE ALSO
 
 .PP